If they find it then maybe. There is no reason to hide the links from what you are telling us. As long as you are not using some awful JavaScript links in your nav then you should be fine. Add ALT attributes to the graphical buttons. If you are worried about spidering, also add some closing text links at the bottom of each page.

No. It is for the Users. I wil have a normal nav, but on the top of the page a sort of evidenced menu, with some important links, will appear and it will have some js frills (moofx stuff), even though it will be completely W3C compliant.. I will replace some texts with some pngs reading the same texts.

I think it won't be banned, since a ban should come from a human checker. But, will I be penalised?